In electrophotography or in ionography a charge image is generated by selectively discharging a homogenous precharged insulating surface of a recording member, onto which toner is deposited. The developed toner image is then transferred to a sheet or web of paper with an electrostatic field. After the developing process, the toner image could be easily disturbed by mechanical effects. Therefore, the toner image is fixed to the paper by heat and pressure. Typically the paper is transported in a nip between a fuser and a pressure roller, which are rotating. Inside the fuser roller or inside heater rollers contacting the fuser roller a heating lamp is installed. The thermal radiation of the lamp heats the surface of the fuser roller or the surface of the heater rollers. The thermoplastic toner on the paper becomes liquid and is pressed into the paper fibers. The fibers act as a capillary system into which molten toner can flow. If the fuser roller stops rotating in an error situation, it would lead to overheating. An overheat condition could lead to freezing the roller bearings or cause the roller break. Therefore motion sensors are required to ensure that a fuser roller does not stop rotating in a standby mode or that the fuser is shut down if the fuser roller stops rotating.
It is well known to use a magnetic sensor to detect a metal tab attached to an end of a heater roller. The magnetic sensor incorporates it's own internal magnetic field. As the heater roller rotates, the passing metal tab distorts the magnetic field. The magnetic sensor changes it's logic state every time the metal tap passes to indicate the heater roller is rotating. The position of the magnetic sensor to the metal tab is critical. This means much effort to adjust the sensor so that a proper signal is obtained. To adjust the sensor mounting brackets and adjusting screws are required which adds cost to the assembly not only for the material but also the labor.
It is an object of the present invention to develop a device for treating the surface of an article in connection with printing including a motion sensor for at least one rotating element, whereby the sensor, it's mounting elements and the adjusting are less cost intensive.
It is another object of the present invention to increase the reliability of the motion detection to prevent failures of a printing device including a printing material treating device.